Electrode structure



Dec. 11, 1951 COLEMAN 2,578,044

ELECTRODE STRUCTURE Filed June 28, 1947 2 Sk-IEETS-Sl-IEET 1 1951 E. D. COLEMAN 2,578,044

ELECTRODE STRUCTURE Filed June 28, 1947 2 SHEETS-SHEET 2 9 2| I 9% /l ij. 29 49 d -[J 46 c j 30 l v q. i 1 v a! a; H \i 45 1! 42 l 5 ff" 7 T,

Patented Dec. 11, 1951 UNITED STATES i ATENT OFFICE ELECTRODE STRUCTURE Edwin D. Coleman, Maywood, Ill.

Application June 28, 1947, Serial No. 757,743

7 Claims.

This invention relates to potential measuring instruments and more particularly to an ion activity measuring instrument having a portable electrode support shaped to receive electrodes adapted for insertion in a solution so as to form a cell.

An object of the invention is to provide a device of the above character with means for precluding leakage currents between one of the electrodes and the electrode support or sample.

A further object of the invention is to provide a device of the above character having a portable electrode support with electrodes secured thereto that are readily and easily replaceable.

Another object of the invention resides in the provision of a novel construction of the electrodes and the electrode support.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a transverse sectional view of the electrode support showing the electrodes connected to a potential determining circuit;

Fig. 2 is a top view of the electrode support;

Fig. 3 is taken along the axis 33 of Fig. 2;

Fig. 4 is a sectional View taken along the line 4-4 of Fig. 2, and

Fig. 5 is a sectional view taken along the line 5-5 of Fig. 2.

Referring now to the drawings, the invention is shown embodied in an electrode assembly of an instrument utilized in determining the hydrogen ion acivity of a solution. As shown in Figure 1 the assembly comprises a portable body ll of insulating material to which is secured a glass electrode l2 having an end terminal [2a and a reference electrode i3 having a terminal l3a at its upper end. The electrodes are arranged for electrical connection to a potential determining circuit designated generally by the numeral l5 by conductors l8 and I9 respectively.

The body H as shown in Figs. 2 and 3 comprises a cup-shaped housing, formed by a circular-shaped bottom member 26, a side wall 2!, and a top member 22. On the interior of the housing is a chamber 23 for the contact elements 24 and 25. The latter provide a connection between the electrodes [2 and i3 and the conductors l8 and I9 respectively. The contact elements comprise elongated flat springs 26 and 21 spaced apart and secured at one end in a cantilever fashion (see Figs. 4 and 5) to bosses 29 and 30, integral with the bottom member 20,

by screws 32 and 33 respectively. The springs are arranged so that their free ends are engage-.- able with the electrode terminals [2a and 13a respectively. Due to the resiliency of the springs, it will be apparent with this construction, that a good wipin contact is assured between the respective contact elements 24 and 25 and the terminals.

The conductors l8 and I9 connect contact elements 24 and 25 With'phone tips 34 and 35 respectively. The conductors may be of any desired length so that measurements of the ion activity of the solution can be ascertained at points remote from the potential measuring circuit. To prevent damage to the conductors l8 and i9 and at the same time provide an insulae tion for the conductors, the latter are onsheathed in an insulating tube 38. As shown in Fig. 3, the conductors l8 and I9 enter the housing through a metallic sleeve 39 which forms a mechanical protection for the conductors. One end of the sleeve is threaded into the sidewall 2i of the support H and the opposite end forms an anchor for the tubing 38. Although not always necessary, in the present embodiment of the invention the metallic sleeve 39 is insulated from contact with external sources by a sleeve 40 of insulating material intermediate the support H and the tubing 38.

One aspect of my invention is concerned with the use of electrodes that may be quickly in,- serted and readily removed from the portable support II, and when inserted are firmly ret ned in posit 0 hat t e le r e may e inserted in a solution to iorm a cell. Thus, it contemplates the use of electrodes having bases that are insertible in openings formed in the body II. Herein the electrodes 12 and 13 have mounting sleeves or bases M and 42 respectively at one end, fashioned from insulating material, such as Bakelite, and formed with a threaded portion designed to interfit with threaded openings .43 and 54 on the bottom member '20 of the support II so that they can be screwed in until the terminals 211 or i3a engage the contact elements 24 and 25. With this construction it will be apparent that the electrodes are held in fixed relationship and may be readily removed or re: placed. Thus the utility of the support isgreatly enhanced since the support can be utilized with a variety of electrodes such as may be required in testing various types of solutions. To provide a good gripping surface for manual handling of the electrodes while installing or removing the same, the sleeve of each electrode is roughened such as by fashioning axially extending grooves on the outer periphery of the respective bases.

In making measurements of this character, it is important that all electrical leakage be avoided. In the use of glass electrodes such as the glass electrode I2 wherein the resistance of the glass itself may be in excess of 100 megohms, it has been found that the insulation material em bracing the electrode and forming the base 4| is not entirely dependable in eliminating the leakage of current between the glass electrode 1 2 and the body I l. Accordingly, my invention is directed to providing means for preventing leakage between the electrode and the'electrode support. For this purpose I utilize an electrical shielding conductor between the base 4| of the electrode [2 and the body H, between the contact element 24 and the body H, and between the conductor [8 and the body I I, and then maintain this electrical conductor at a potential equal to that of the contact l2a at the instant of taking a measurement. Since a difference of potential must exist before there can be any leakage of current, there can be no electrical leakage under the conditions specified above between the electrode or its associated conductor l8 and the body ll.

As shown in Fig. 4 part of the shielding conductor takes the form of a threaded brass insert forming a guard ring 45 in the bottom member 2|] of the support ll, disposed so as to form a liner for the opening 43 and a receptacle for the electrode l2. The shielding conductor also includes a brass ring 46 embracing the boss 29 intermediate the contact element 24 and the bottom 20.

The shielding conductor between the conductor 3 and the body ll comprises a metallic braid 49 encircling the insulation covering the conductor l8. At one end of the conductor l8, the braid 49 is connected to a phone tip 50 for connection to ground M as will hereinafter be more fully described. At the opposite end of the conductor, the braid 49 is exposed in the chamber 23, formed in the body I I, for connection to a metallic spring strip 52 (see Fig. 2) which is sprung into contact with the guard ring 45, the ring 46, and the exposed portion 53 of the braid by an upstanding lug 54 of insulating material.

An suitable means may be used for applying potential to the shielding conductor so long as the potential of the shielding conductor is that of the glass electrode terminal l2a at the instant of making measurements. In this embodiment of the invention the circuit shown in Figure 1 and utilized for measuring the potential or ion activity of a solution under test is used to effect the foregoing. Briefly, this circuit comprises a potentiometer circuit 55 associated with an impulse type amplifier circuit 56 interconnected with the electrodes I2 and I3 to determine the potential developed between the latter. The potentiometer circuit comprises a variable resistance 51 connected in parallel with a variable resistance 58 and a battery 59 connected in series. The impulse amplifier circuit includes a vacuum tube 60, the plate of which is connected to a meter 6| and a battery 62 connected in series and the grid of which is connected to a condenser 63. Voltage for the filament of the tube 60 is supplied by a battery 64.

In Figure 1 the potentiometer circuit 55 is connected to the reference electrode l3 through a slider 65 on the variable resistance 51 in the potentiometer circuit, a conductor 66, the phone tip 35, and the conductor l9. The potentiometer circuit is also connected by a conductor 67 to the impulse type amplifier circuit 56, the latter being connected to electrode [2 through the condenser 63, a conductor 68, a switch 69, a switch contact 69a, a conductor H, the phone tip 34, and the conductor I8. The latter side of the potentiometer circuit is also connected to a contact 6912 on the switch 69 and to a so-called McClure ground M through a conductor 12.

The potential developed in the potentiometer circuit is opposed to that developed between the electrodes l2 and I3. By varying the position of the slider 65 on the resistance 51 in the potentiometer circuit the potential thereof can be made to be exactly equal and opposite to that developed between the electrodes. The impulse type amplifier circuit 56 is associated with the potentiometer circuit in such a manner as to compare the potential of the potentiometer circuit with that developed between the electrodes [2 and Hi. When the two potentials are equal and opposite (as determined by alternately moving the blade of the switch 69 between contacts 69a and 69b and no deflection of the needle occurs in the meter 6!), readings are taken. Preferably, the potentiometer is calibrated to indicate directly the potential of the cell, the pH of the solution under test, or other desired data, as required.

As shown in Figure 1, one side of the potentiometer circuit is connected to ground M through conductor 12. Since the shielding conductor comprising the circuit beginning with the guard ring 45, the ring 46, the metallic strip 52, the metallic braid 49, the phone tip 50, and a conductor 13 is connected to ground M, the potential of the shielding conductor is also determined by the potentiometer circuit. Thus, when the readings are taken, that is, when no defiec tion occurs on the needle of the meter 6!, the potential of the shielding conductor will be that of electrode terminal i2a. Since a difference of potential must exist before there can be any current leakage, there will be no leakage between the electrode [2 and the body II, the electrode contact 12a and the body I I, or between the contact element 24 and the body ll, because the shielding conductor is at the same potential as the electrode terminal lZa at the instant of taking a reading.

I claim:

1. An ion measurement electrode comprising in combination, a pair of surement electrodes each having an electrical terminal at one end and an annular mounting sleeve adjacent said end for manual handling of theelectrode, a rigid body of electrical insulating material having openings on the bottom surface thereof receiving said mounting sleeves from the bottom of the body, means acting between the body and the electrodes for releasably securing the electrodes to the body, a guard ring of electrically conductive material mounted on the body and interposed between the body and one of said electrodes and encircling the latter, contact elements mounted on the body and positioned for engagement by said terminals upon insertion of the electrodes into the body, and a flexible cable including insulated electrical conductors for attachment to a measuring instrument, two of the conductors being connected to said contact elements and another of the conductors being electrically connected to said guard ring and encircling the conductor attached to the structure ion meacontact element associated with the guard ring s'ubstantiallythroughout the length: thereof, said another conductor adapted to be connected to ;a source of potential having the same value as that to be measured to prevent. leakage between the respective parts at the instantof taking a measurement.

2. In a portable electrode support, the combination of a portable base of insulating material having'threaded recesses, opening on the bottom surface, one of said recesses having a liner of conducting material, an electrode removably threaded into each of said recesses from the bottom of the base, a first electrical conductor mounted on said base electrically connecting the electrode inserted in the recess with the liner to a measuring instrument, a second electrical conductor mounted on said base electrically connecting the other electrode to said measuring instrument and conductor means electrically connecting said liner to said instrument, said means being shaped to form a shield for the first conductor throughout its length and adapted to be connected to a source of potential having the same value as that being measured to preclude leakage between the electrode and the body.

3. In a portable electrode assembly, the combination of a housing of insulating material having a chamber formed therein and a pair of bottom openings, one of said openings having an insert of conducting material, a pair of contact elements mounted in said chamber and each disposed adjacent one of said openings, a pair of electrodes having terminal portions releasably mounted in the housing through said bottom openings and insertable to a position in which said terminal portions are disposed in said chamber to engage the respective contact elements, and a flexible cable fixed to the housing comprising a first conductor connected to the contact element adjacent the insert for connecting it to a measuring instrument, a second conductor connected to the other of said contact elements for connecting it to said measuring instrument and a third conductor for connection to said instrument connected to the insert and forming a shield for the first conductor throughout its length.

4. In a portable electrode assembly, the combination of a body having threaded bottom openlngs, one of said openings having a conducting liner rigid with the body, a first contact element mounted on said body adjacent the opening with the liner, a second contact element mounted on said body adjacent another of said openings, a pair of electrodes received in said openings from the bottom of the assembly engaging said contact elements, means acting between said electrodes and said body for releasably securing said electrodes to the body, a guard ring mounted on the body for the first contact element disposed between said contact element and the body, and a flexible cable fixed to said body comprising a first conductor for connecting the first contact element to a measuring instrument, a second conductor for connecting the second contact element to said measuring instrument and metallic sheath means for the first conductor electrically connected with said liner and said guard ring and adapted for connection to said instrument.

5. In a portable electrode assembly, the combination of a housing of insulating material having a chamber formed on its interior and having spaced bottom openings, a conducting insert fixed in one of said openings, a first cantilever mounted contact element in said chamber overlying the opening having the insert and in spaced relation thereto, a second cantilever mounted contact'eler' ment in said chamber overlying the other open-' ing, a pair of electrodes mounted in said'body each having an electrical terminal at oneendandan annular mounting sleeve adjacent said end for manual handling of the electrode, said sleeve having a portion shaped for insertion into. said chamber through said bottom openings of the housing to effect contact between the terminals of each electrode and a contact element, means acting between said sleeve and said housing for releasably securing each electrode to the body, conducting means in said chamber disposed between the first contact element and the housing, a first conductor connected to said first contact element, a second conductor connected to said second contact element and a conducting sheath surrounding the first conductor and electrically connected to said insert and to said conducting means in said chamber, said first and second conductors and said conducting sheath being insulated from each other and enclosed within a common insulation to form a cable for connecting the electrode assembly to an instrument.

6. A portable electrode structure for ion measurement comprising a body of insulating material having an enclosed chamber and a bottom opening communicating with said opening, a ring of electrically conductive material fixed to the body within said opening forming an electrical guard ring, an electrode mounted on said body and insertable upwardly into said bottom opening, means acting between said body and said electrode for releasably securing the electrode in said opening, an electrical connecter mounted in said chamber for engagement by said electrode upon insertion thereof into said opening, a shield mounted in said chamber for shielding said connector, a flexible cable, and means for afiixing the cable to said body, said cable including insulated electrical conductors for attachment to a measuring instrument, one of said conductors being electrically connected to a terminal of said electrode and a second of the conductors being electrically connected to said guard ring and encircling the first-mentioned conductor substantially throughout the length of the latter, said second conductor and the guard ring being adapted to be connected to a potential of the same value as that to be measured whereby to prevent leakage between the respective parts at the instant of taking the measurement.

7. In a portable electrode assembly of the type having the ion measurement electrodes of an ion measurement cell, the combination of a housing of insulating material enclosing a chamber and having spaced bottom openings shaped for the reception of the electrodes, a conducting insert fixed in one of said openings forming an electrode guard ring, a first cantilever mounted contact element in said chamber overlying and in spaced relation to that one of the openings having the aforesaid insert, a second cantilever mounted contact element in said chamber spaced from and overlying the other opening, means for releasably securing electrodes on the body in the aforesaid openings in depending relation thereto, conducting means in said chamber disposed between the first contact element and the housing, a first conductor electrically connected to said first contact element, a second conductor electrically connected to said second contact element 7 and an electrically conducting sheathsurrounding the first conductor, electrically connected to said insert and to the aforesaid conducting means in said chamber, said first and second conductors and said conducting sheath being insulated from each other and enclosed within a common insulation to form a cable for connecting the electrode assembly to an instrument.

EDWIN D. COLEMAN.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number 8 UNITED STATES PATENTS Name Date I Coleman Feb. 23, 1943 Coleman Aug. 28, 1945 Ingalls June 11, 1946 FOREIGN PATENTS Country Date Germany May 10, 1937 

